This project represents a joint endeavor between the Harvard Community Health Plan, a health maintenance organization, and the Laboratory of Computer Science of the Massachusetts General Hospital, for the purpose of developing an operational quality assurance program based on computerized ambulatory record (COSTAR) system. The objectives of this project include the development of methodologies for assessing and improving compliance with process and outcome criteria, which meet the requirements of the Federal HMO Act; a demonstration of the utility of the COSTAR system for both audit and feedback; and an assessment of the impact on provider and system behavior of several quality assurance feedback mechanisms regarding inadequate compliance with established standards.